Radiation-sensitized fine-grained silver halide photographic sensitive material

ABSTRACT

A radiation-sensitive silver halide photographic emulsion containing silver halide crystals whose mean grain size is not greater than 0.2 micron or at least 90% in number of which are not greater than 0.25 micron in grain size and at least one sensitizing base represented by the following general formula (I);   wherein Z1 and Z2 each represent the atoms necessary to form a benzene ring, Y represents an oxygen atom, a sulfur atom, a selenium atom or &gt;N-R1, Y&#39;&#39; represents a sulfur atom, a selenium atom or &gt;N-R3, R1 and R2 which may be the same or different, each represents an alkyl group, R3 represnts a hydrogen atom or an alkyl group, and n represents 1 or 2.

United States Patent [1 1 Nakamura et al.

[ RADIATION-SENSITIZED FINE-GRAINED SILVER HALIDE PHOTOGRAPHIC SENSITIVE MATERIAL [75] Inventors: Yasuharu Nakamura; Yoshiyuki Nakazawa; Tohru Sueyoshi; Akira Sato, all of Kanagawa, Japan [73] Assignee: Fuji Photo Film Co., Ltd.,

Kanagawa, Japan [22] Filed: Apr. 12, 1973 [21] Appl. No.: 350,579

[30] Foreign Application Priority Data Apr. 12, 1972 Japan 47-36676 [52] US. Cl. 96/137; 96/133; 250/475 [51] Int. Cl. G03c 1/18; G03c 1/20 [58] Field of Search 96/137, 132, 133

[56] References Cited UNITED STATES PATENTS 2,393,743 1/1946 Brooker et a1 96/137 2,918,369 12/1959 Doorenbos 3,090,782 5/1963 Coenen et al..... 3,706,566 12/1972 Shiba et a1. 3,706,570 12/1972 Nakazawa et al .t 96/137 June 17, 1975 Primary Examiner.l. Travis Brown Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn and Macpeak [57] ABSTRACT A radiation-sensitive silver halide photographic emulsion containing silver halide crystals whose mean grain size is not greater than 0.2 micron or at least 90% in number of which are not greater than 0.25 micron in grain size and at least one sensitizing base represented by the following general formula (1);

CN 1 C QJ L (I) 20 Claims, No Drawings RADIATION-SENSITIZED FINE-GRAINED SILVER HALIDE PHOTOGRAPI-IIC SENSITIVE MATERIAL BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiationsensitized silver halide photographic emulsion and, more particularly, to a silver halide photographic emulsion containing fine-grained silver halide crystals sensitized with certain cyanine bases.

2. Description of the Prior Art In the art of producing silver halide photographic light-sensitive materials, it is well known to extend the light-sensitive wave-length region by adding a sensitizing dye to a silver halide photographic emulsion. However, in general, when a silver halide photographic emulsion containing silver halide crystals of the grain size usually used for the production of silver halide photographic light-sensitive materials is subjected to a spectral sensitization, the sensitivity in the absorption wave-length region intrinsic to silver halide is reduced. This phenomenon is well known as desensitization due to a sensitizing dye.

Therefore, as a sensitizing dye to be used for the production of a silver halide photographic light-sensitive material, one which exerts a low desensitization is desired.

On the other hand, in order to improve the image quality of a silver halide photographic light-sensitive material, it is preferred to minimize the grain size of silver halide crystals contained in the silver halide photographic emulsion as much as possible. However, this will result in a reduction in sensitivity.

Intensive research in this art has been conducted to produce a silver halide photographic light-sensitive material having sufficient sensitivity by chemical sensitization, such as sulfur sensitization utilizing thiourea derivatives, sodium thiosulfate or the like reduction sensitization utilizing stannous chloride or hydrazine, and gold sensitization utilizing salts of gold, platinum or a like noble metal, while minimizing the grain size of silver halide crystals as much as possible.

As methods of sensitizing a radiation-sensitive material for use in electron beam recording, these known sensitizing methods are not sufficient.

Electron beam-recording enables one to record with high density, but in order to obtain an image of high quality, it is firstly necessary to minimize the grain size of the silver halide in the light-sensitive material as much as possible. However, a reduction in the grain size of the silver halide generally results in a reduction in the sensitivity to electrons. Therefore, a novel sensitizing method becomes necessary. Secondly, it is of importance to reduce the surface charge of the lightsensitive material irradiated with electrons to form a distinct image. For this purpose, it is necessary to raise the velocity of electron beam recording to reduce the amount of irradiation with electrons. From this viewpoint, a light-sensitive material having high sensitivity to electron beam is also required.

As is described above, in the production of radiationsensitive materials for use in recording electron beams a silver halide photographic emulsion wherein the grain size of the silver halide crystals is minimized as much as possible and yet which has high sensitivity to electron beams is required. It has become of great interest to the art to sensitize emulsions to electron beams.

However, with respect to dyes effective for emulsions of the usual grain size or effective with usual light, the effects thereof cannot be anticipated at all when finegrained emulsions and electron beams are employed.

SUMMARY OF THE INVENTION It is, therefore, one object of the present invention to provide a silver halide photographic emulsion having, even when chemically sensitized, enhanced sensitivity in the absorption wave-length region intrinsic to silver halides.

Another object of the invention is to provide a highly radiation-sensitive photographic emulsion providing improved image quality.

Another object of the invention is to provide a photographic emulsion having an extended light-sensitive wave-length region.

Another object of the invention is to provide a silver halide photographic emulsion which solves the abovedescribed problems.

The inventors havefound that when a silver halide photographic emulsion containing silver halide crystals whose mean grain size is not greater than 0.2 micron, or at least in number of which are not greater than 0.25 micron in grain size, is spectrally sensitized with a certain cyanine base, not only is the light-sensitive wave-length region extended, but also the sensitivity in the absorption wave-length region intrinsic to silver halide is remarkably enhanced, and that the sensitivity of a silver halide photographic emulsion to electrons can be markedly raised by incorporating one or more of such bases in the emulsion.

One known procedure where the light sensitivity in the absorption wave-length region intrinsic to silver halide is raised by a sensitizing dye is the Capri blue effect. However, the Capri blue effect appears when a sensitizing dye is added to a silver halide photographic emulsion which has not been subjected to sulfur sensitization or reduction sensitization.

The effect discovered in the present invention is absolutely different from the Capri blue effect in that even when a silver halide photographic emulsion containing silver halide crystals of a specific grain size is subjected to sulfur sensitization, reduction sensitization or gold sensitization, the light sensitivity of the emulsion in the absorption wave-length range intrinsic to silver halide can be simultaneously enhanced when the emulsion is spectrally sensitized with a cyanine base represented by the later described formula.

The above-described objects of the invention are attained by incorporating in a photographic emulsion of silver halide crystals whose mean grain size is not greater than 0.2 micron, or at least 90% in number of which are not greater than 0.25 micron in grain size, at least one cyanine base represented by the following general formula;

used those generally known for benzimidazolocarbocyanines, such as a halogen atom, (e.g., fluorine atom, chlorine atom, bromine atom, etc.), a trifluoromethyl group, an alkylsulfonyl group, wherein the alkyl moiety preferably has up to 4 carbon atoms (e.g., methylsulfonyl group), an aminosulfonyl group (e.g., sulfo- 1O nyl, methylaminosulfonyl, morpholinosulfonyl, pyrrolidinosulfonyl group, etc.), a cyano group, a carboxyl group, an alkoxycarbonyl group, wherein the alkyl moiety preferably has up to 3 carbon atoms (e.g., methoxycarbonyl, ethoxycarbonyl group, etc.), an acyl group (e.g., an aliphatic acyl such as acetyl, an aromatic acyl group such as a benzoyl group, etc.) and the like. Of these, a chlorine atom is preferred.

As the substituents on the group Z there can be the alkyl moiety preferably has up to 3 carbon atoms (e.g., beta-cyanoethyl, gamma-cyanopropyl, deltacyanobutyl, etc.), carbamoylalkyl, wherein the alkyl moiety preferably has up to 4 carbon atoms (e.g., betacarbamoylethyl, gamma-carbamoylpropyl, deltacarbamoylbutyl, beta-N-ethylcarbamoylethyl, gamma-N-ethylcarbamoylpropyl, delta-N-methylcarbamoylbutyl, etc.), sulfamoylalkyl wherein the alkyl moiety preferably has up to 4 carbon atoms (e.g., gamma-sulfamoylpropyl, delta-sulfamoylbutyl, gamma- N-ethylaminosulfonylpropyl, delta-N- ethylaminosulfonylbutyl, etc.), sulfoalkyl, wherein the alkyl moiety preferably has up to 4 carbon atoms (e.g., beta-sulfoethyl, gamma-sulfopropyl, delta-sulfobutyl, etc.), aralkyl, wherein the alkyl moiety preferably has up to 2 carbon atoms (e.g., p-carboxybenzyl, p-carboxyphenethyl, p-sulfobenzyl, p-sulfophenethyl, benzyl, phenethyl, etc.), vinylmethyl, etc., where R and R may be the same or different from each other, and R used an alkyl group, preferably having up to 4 carbon represents a hydrogen atom, an alkyl group, preferably atoms (e.g., methyl, ethyl group, etc.), a halogen atom (e.g., fluorine, chlorine, bromine, etc.), an alkoxy group, wherein the alkyl moiety preferably has up to 3 carbon atoms (e.g., methoxy group, etc.) and the like.

Y represents an oxygen atom, a sulfur atom, a selenium atom or an N---R group and Y represents a sulfur atom, a selenium atom or an NR group, where R and R each represents an alkyl group (i.e.,

unsubstituted alkyl and substituted alkyl, e.g., methyl,

having up to 4 carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), and n represents 1 or 2.

When one of R and R contains as a substituent a sulfo group or a carboxyl group, for example, a gamma- 1 .11 CH Crl Cl1 SO The sensitizing bases most effective to increase the ethyl, n-propyl n-butyl group, hydroxyalkyl, wherein sensitivity of the emulsion to electrons are those reprethe alkyl moiety preferably has up to 4 carbon atoms sented by the following generaLformula (III);

wherein Y" represents a sulfur atom or a NR group; Z Z R R R and n each have the same meanings as defined in general formula (1).

Typical examples of cyanine bases represented by the general formulae (I), (II) and (III) used in the invention are illustrated helon. However, the invention is not to be limited thereto. Dye:

The sensitizing bases represented by general formula (I) can be synthesized by refluxing a compound repre- C C\ (V) sented by the following general formula (IV) and a 2 1- 2 compound represented by the following general for- 50 mula (V) in alcohol in the presence of triethylamine according to a method described in the textbook by F. R M. Hamer (The Chemistry of Heterocyclic Com- 2 pounds: The Cyanine Dyes And Related Compounds, lnterscience Publishers): 55

h COCn I R (X') wherein Z and Y are the same as defined above. Generally, synthesis is under the following reaction conditions: molar ratio of reactants: stoichiometric amount; temperature: on a water bath; time: within 1 hour; pres sure: atmospheric; amount of alcohol: sufficient to dissolve reactants; triethylamine: as shown in the Synthesis example.

SYNTHESIS EXAMPLE Base (3):

1,3 Grams of Z-beta-acetanilidovinyl-S,6-dichloro- 1,3-diethylbenzimidazolinium iodide was refluxed for 15 minutes together with 0.5 g of 2- cyanomethylbenzimidazole in 50 ml of ethanol in the presence of 3 ml of triethylamine over a water bath to complete the reaction. Crystals were precipitated during the reaction. After cooling, the reaction product was filtered out, then washed with hot ethanol. Thus, there was obtained 0.7 g of the end product having a melting point of above 300C.

Other dyes can be synthesized following this basic synthesis method merely by altering the starting materials.

By the present invention, not only is the lightsensitive wave-length region of a silver halide photographic emulsion extended, but the light sensitivity in the absorption wave-length region intrinsic to silver halides is remarkably enhanced as well.

This effect is particularly conspicuous with a gelatino-silver halide photographic emulsion. However, the present invention is effective also in silver halide photographic emulsions containing other synthetic or natural hydrophilic high molecular weight polymer binders which do not harm photographic properties such as gelatin derivatives (e.g., acetylated gelatin, malonated gelatin, phthaloylated gelatin, etc.), a water-soluble cellulose derivative (e.g., hydroxyethyl cellulose, carboxymethyl cellulose, etc.) hydrophilic polymers (e.g., polyvinyl alcohol, polyvinyl pyrrolidone, polystyrene sulfonic acid, polyacrylamide) and the like. The ratio by weight of silver halide to hydrophilic binder is preferred to be within a range of from about A to about 4/1.

The sensitizing effect in the absorption range intrinsic to silver halide in the invention depends greatly upon the grain size of the silver halide crystals used. That is, in silver halide photographic emulsions having the same halogen composition andd the same base, the effect varies depending upon the grain size of the silver halide crstals. In a silver halide photographic emulsion containing silver halide crystals whose mean grain size is greater than 0.2 micron, e.g., 0.6 micron, there is observed little or no sensitizing effect.

As a specific example, the relationship between the mean grain size of the silver halide crystals and the sensitizing effect with respect to the case of using Base (5) is tabulated below.

The sensitization ratios are shown in terms of relative ratios based on the sensitivity value of a silver halide photographic emulsion containing no Base (5), which value is taken as l.

The mean grain size can be determined in a Conventional manner, e.g., measuring the projected area as described in The Photographic Journal, vol. LXXIX, pp.330-338 (1939).

From Table 1, it can be seen that the influence of the grain size of the silver halide crystals on the sensitizing effect of the invention is extremely great.

The radiation-sensitive silver halide used in the invention can be any of silver chloride, silver bromide, silver chlorobromide, silver bromoiodide and silver chlorobromoiodide. In particular, an excellent effect is exhibited in the case of silver bromide and silver bromoiodide.

In order to prepare a spectrally sensitized silver halide photographic emulsion, one or several bases represented by the general formula (I) can be added in a conventional manner to a silver halide emulsion. The emulsion can be previously chemically sensitized in a conventional manner, such as by gold sensitization (e.g., see U.S. Pat. Nos. 2,540,085; 2,597,856; 2,597,9l5; 2,399,083, etc.) by Group VIII metal ion sensitization, sulfur sensitization (e.g., see U.S. Pat. Nos. 1,574,944; 2,278,947; 2,440,206; 2,410,689; 3,189,458; 3,415,649, etc.), by reduction sensitization (e.g., see U.S. Pat. Nos. 2,518,698; 2,419,974; 2,983,610, etc.) or a mixture thereof. It is preferred to chemically sensitize the emulsion with a liable sulfur compound and a gold complex salt, but the photographic emulsion need not necessarily be previously subjected to chemical sensitization.

The base(s) can be added to a silver halide photographic emulsion as a solution prepared by dissolving the bases in a suitable solvent such as methanol, ethanol, methyl cellosolve, etc. The amount of the base(s) incorporated can be varied over a wide range, for example, of from about 1X10 to about 1X10 mol/mol Ag.

As indicated, the compositional bounds set out above are not mandatory in the present invention. However, as one begins to use much lower concentrations of the sensitizing dye the sensitizing effect gradually reduced. On the other hand, using greater amounts of sensitizing dye does not appreciably increase or conversely decreases the sensitizing effect and is economically wasteful.

The silver halide photographic emulsion of the invention can further be supersensitized or hypersensitized.

The sensitizing effect of the present invention can be obtained, in one embodiment, by adding the sensitizing base to a silver halide photographic emulsion prepared in a usual manner immediately before applying the emulsion to a support. However, similar effects can be obtained by adding the sensitizing base during physical ripening or chemical ripening, etc. There is no restriction as to the stage of the addition of the base.

In the production of the silver halide photographic emulsion of the invention, usually employed additives such as other chemical sensitizing agents, a stabilizer, an anti-fogging agent, a toning agent, a hardener, a surface active agent, a thickener, a plasticizer, a lubricant, a development accelerator, a color coupler, a brightening agent or the like can be added in a conventional manner and in conventional amounts.

The present invention will now be described in greater detail by the following non-limiting examples of preferred embodiments.

EXAMPLE 1 To g of a chemically repened gelatino silver bromoiodide Br: 99 mol I:1 mol emulsion (gelatino: silver halide 1:1 by weight) containing silver halide crystals of 0.07 micron or 0.6 micron (for comparison) in mean grain size (prepared in a known manner) were added, respectively, methanol solutions of bases in the amounts shown in Table 2. Chemical sensitization was performed with triethyl thiourea and potassium chloroaurate. mg. triethyl thiourea per mole of silver, 1 mg. potasium chloroaurate per mol of silver. 7 milliliters of the thus produced silver halide photographic emulsions were applied to cabinet-sized glass plates and dried to prepare samples.

The resulting samples were exposed to a tungsten 14 I EXAMPLE 2 A gelatino silver bromide emulsion (gelatin: silver halide=l:l by weight) containing silver bromide grains having a mean grain size of a 0.08 micron was prepared g a K gl gifi i a i according to the known Lippmanns method (P.Glafki- 47 d t t z g dis; Photographic Chemistry, vol. 1, 365-368) an 3 Su th F n in f l and subjected to sulfur sensitization and gold sensitiza- .mmutes m eve oper avmg e o Ow g tion according to Example 1 and the divided into 12 portions.

One portion was used as such, and to each of the other 11 portions was added a definite amount of a g 2 2 methanol solution of a sensitizing base of the invention. g s iu sumte 96 Each of the resulting portions was applied to a cellulose 14 A h d l' g 2 l 5 triacetate film base and dried to prepare test samples. 2 n y ,,i; f* 5 After irradiating the samples with electron beams at an liter. Water to make 1 acceleration voltage of KV and at an electric current density of 10 to 10 coulomb/cm using an electron beam generating apparatus, the samples were c The results Obtained are Shown in Table 20 SUbJCtd to development at 20 C for 4 minutes using a developer havmg the following formulatlon. Charac- The sensitization ratios are shown in terms of relative teri ti urves were determined for the samples. ratios based on the sensitivity value in the absorption range intrinsic to silver halide not containing a sensitizing base, which value was taken as l. Mew] g From Table 2, it can be seen that, in the case of the yd us sodium sulfite mg g i Hydroqumone 5 g photographic emuls1on of the present 1nvent1on con- Borax 2 g taining silver halide crystals of not greater than 0.2 mi- Water 10 make 1 liter cron in mean grain size and containing a base of genera] formula (I), the sensitization ratio in the absorp- The results obtained are shown in Table 2. tion region intrinsic to silver halide is remarkably high. In Table 2, the photographic sensitivity is relatively Also, in the case of silver halide crystals of grains at shown by determining the irradiation amount required least 90% in number of which are not greater than 0.25 for the foog-free photographic density to go up to 0.5 micron in grain size, a markedly high sensitization ratio while taking the (sensitivity value of a sensitizing basewas similarly obtained. free emulsion as 100.

Table 2 Sensiti- Sensiti zation Mean zation Mean ratio grain ratio Sensi- Amount of grain (in the size (in the tizing mol of base added size jm i (for intrinsic base (mol of base (present absorp compaabsorp-.

mol of Ag) invention) tion range None (Control) 0 0.070 1 0.6 l

2.4 1o-' 0.07 11.2 0.611. 4. 1.2x10- 0.0m 8.5 0.6 1.0

2.4Xl0 0.07;. 9.5 0.6 5 12x10 0.07 1. 8.0 0.6 0.5

2.4X10 0.07 1. 9.0 0.611. 1.2 10- 0.07;.t 8.8 0.6;; 08 24x10 0.0m 11.6 0.6;2 8. l.2 l0 0.07 4 5.0 0.6;. 0.3

2.4 10- 0.0m 15.5 0.6 1. l0. l.2Xl0* 0.07 1. 12.1 0.611. 0.2

2.4Xl0 0.07;]. 9.5 0.61.1. 11. 11x10 0.0m 6.5 0.6 .1. 0.3

2.4 10- 0.0m 7.2 0.6 12. 1.2x10- 0.0m 8.0 0.61.1. 0.1

2.4x10 0.07 12.0 0.6 1. l4. 1.2Xl0 0.07 1. 10.6 0.6 0.2

Table 2 Results of electron beam sensitometry Basc Amount added Sensiti- Fog (per 100 g zation of silver) degree None (control) 0 100 0.04

3 320 cc. mol

soln. of base l70 0.05 4 320 cc. 190 0.07 10 320 cc. 160 0.05 5 320 cc. 160 0.04 I2 80 cc. 140 0.04 6 320 cc. 140 0.07 320 cc. 200 0.04 8 320 cc. 180 004 I3 320 cc. l80 0.04 16 320 cc. 170 0.04 l7 320 cc. I80 0.04

As is clear from Table 2, the photographic emulsions of the invention of fine grain size provide high image quality and have a high sensitivity to electrons beams without a substantial increase in fog. Therefore, it can be said that substantial technical progress has been attained by the present invention.

While the invention has been describedin detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

What is claimed is: a

1. A radiation-sensitive silver halide photographic emulsion containing silver halide crystals whose mean grain size is not greater than 0.2 micron or at least 90% in number of which are not greater than 0.25 micron in grain size and at least one sensitizing base represented by the following general formula (I);

wherein Z and Z each represent the atoms necessary to form a benzene ring, Y represents an oxygen atom, a sulfur atom, a selenium atom or a NR group, Y represents a sulfur atom, a selenium atom or a N--R group, R and R which may be the same or different each represents an alkyl group, R represents a hydrogen atom or an alkyl group, and n represents 1 or 2, said sensitizing base enhancing both the spectral sensitivity and the sensitivity in the absorption wave length region intrinsic to said silver halide.

2. A light-sensitive photographic emulsion containing silver halide crystals whose mean grain size is not greater than 0.2 micron, or at least in number of which are not greater than 0.25 micron in grain size, and at least one sensitizing base represented by the following general formula;

3. An electron beam-sensitive photographic emulsion containing silver halide crystals whose mean grain size is not greater than 0.2 micron or at least 90 percent in number of which are not greater than 0.25 micron in grain size and at least one sensitizing base represented by the following general formula;

wherein Y" represents a sulfur atom or N-R and Z Z R R R and n each have the following meaning: Z and Z each represent the atoms necessary to form a benzene ring; R and R which may be the same or different, each represents an alkyl groups, R represents a hydrogen atom or an alkyl group, and n represents l or 2.

4. A light-sensitive photographic emulsion as claimed in claim 2 wherein the sensitizing base is selected from the class consisting of the following bases:

19 20 5. An electron beam-sensitive photographic emulsion 8. The emulsion as claimed in claim 3 wherein the as claimed in claim 3 wherein the sensitizing base is seamount of base(s) is about 1X10 to about 1X10 lected from the class consisting of the following bases: mol/mol of silver in the emulsion.

fz s H N N gIN k/C cH-CH C-C CH3SOZ \N. l H CH2CH2CHCH3 r1 jLECOO T F 2% 2 5 N 1 N w i =cH-c1-1=cl v C 11 6. The emulsion as claimed in claim 1 wherein the 9. The emulsion as claimed in claim 1 where the amount of base(s) is about 1X10 to about 1X10" emulsion comprises gelatin as a hydrophilic binder. mol/mol of silver in the emulsion. 10. The emulsion as claimed in claim 2 where the 7. The emulsion as claimed in claim 2 wherein the 65 emulsion comprises gelatin as a hydrophilic binder. amount of base(s) is about 1X10 to about lXlO 11. The emulsion as claimed in claim 3 where the mol/mol of silver in the emulsion. emulsion comprises gelatin as a hydrophilic binder.

12. A radiation-sensitive silver halide photographic emulsion containing silver halide crystals whose mean grain size is not greater than 0.2 micron or at least 90% in number in which are not gerater than 0.25 micron in grain size and at least one sensitizing base represented by the following general formula (1);

wherein Z, and Z each represent the atoms necessary to form a benzene ring wherein the Z benzene ring is unsubstituted or if substituted is substituted with halogen, trifluoromethyl, alkyl sulfonyl, where the alkyl moiety has up to 4 carbon atoms, aminosulfonyl, where the alkyl moiety has up to 4 carbon atoms, cyano carboxyl, alkoxycarbonyl, where the alkoxy moiety has up to 3 carbon atoms, acyl, or one or more thereof, and the Z benzene ring is unsubstituted or if substituted is substituted with an alkyl group of up to 4 carbon atoms, a halogen atom, an alkoxy group where the alkyl moiety has up to 3 carbon atoms, or one or more thereof, Y represents an oxygen atom, a sulfur atom, a selenium atom or a l IR group, R, or R which may be the same or different, each represents an unsubstituted alkyl group with up to 4 carbon atoms, hydroxyalkyl where the alkyl moiety has up to 4 carbon atoms, acetoxyalkyl where the alkyl moiety has up to 3 carbon atoms, carboxyalkyl where the alkyl moiety has up to 4 carbon atoms, cyanoalkyl where the alkyl moiety has up to 3 carbon atoms, carbamoylalkyl where the alkyl moiety has up to 4 carbon atoms, sulfamoylalkyl where the alkyl moiety has up to 4 carbon atoms, sulfoalkyl where the alkyl moiety has up to 4 carbon atoms, aralkyl were the alkyl moiety has up to 2 carbon atoms, R represents hydrogen or an alkyl grup with up to 4 carbon atoms, and n is l or 2.

13. The emulsion as claimed in claim 12 where 1, if substituted, is substituted with a chlorine atom.

14. The emulsion as claimed in claim 12 where the amount of base(s) is about lXlO' to about l l0' mol/mol of silver in the emulsion.

15. The emulsion as claimed in claim 14 where the emulsion comprises gelatin as a hydrophilic binder.

16. The emulsion as claimed in claim 1 where R represents an alkyl group.

17. The emulsion as claimed in claim 16 wherein R represents an alkyl group of up to 4 carbon atoms.

18. The emulsion as claimed in claim 2 wherein R represents an alkyl group.

19. The emulsion as claimed in claim 18 wherein R represents an alkyl group with up to 4 carbon atoms.

20. The emulsion as claimed in claim 12 wherein R represents said alkyl group with up to 4 carbon atoms. 

1. A RADIATION-SENSITIVE SILVER HALIDE PHOTOGRAPHIC EMULSION CONTAINING SILVER AHLIDE CRYSTALS WHOSE MEAN GRAI SIZE IS NOT GREATER THAN 0.2 MICRON OR AT LEAST 90% IN NUMBER OF WHICH ARE NOT GREATER THAN 0.25 MICRON IN GRAIN SIZE AND AT LEAST ONE SENSITIZING BASE REPRESENTED BY THE FOLLOWING GENERAL FORMULA (1),
 2. A light-sensitive photographic emulsion containing silver halide crystals whose mean grain size is not greater than 0.2 micron, or at least 90% in number of which are not greater than 0.25 micron in grain size, and at least one sensitizing base represented by The following general formula;
 3. An electron beam-sensitive photographic emulsion containing silver halide crystals whose mean grain size is not greater than 0.2 micron or at least 90 percent in number of which are not greater than 0.25 micron in grain size and at least one sensitizing base represented by the following general formula;
 4. A light-sensitive photographic emulsion as claimed in claim 2 wherein the sensitizing base is selected from the class consisting of the following bases:
 5. An electron beam-sensitive photographic emulsion as claimed in claim 3 wherein the sensitizing base is selected from the class consisting of the following bases:
 6. The emulsion as claimed in claim 1 wherein the amount of base(s) is about 1 X 10 3 to about 1 X 10 5 mol/mol of silver in the emulsion.
 7. The emulsion as claimed in claim 2 wherein the amount of base(s) is about 1 X 10 3 to about 1 X 10 5 mol/mol of silver in the emulsion.
 8. The emulsion as claimed in claim 3 wherein the amount of base(s) is about 1 X 10 3 to about 1 X 10 5 mol/mol of silver in the emulsion.
 9. The emulsion as claimed in claim 1 where the emulsion comprises gelatin as a hydrophilic binder.
 10. The emulsion as claimed in claim 2 where the emulsion comprises gelatin as a hydrophilic binder.
 11. The emulsion as claimed in claim 3 where the emulsion comprises gelatin as a hydrophilic binder.
 12. A radiation-sensitive silver halide photographic emulsion containing silver halide crystals whose mean grain size is not greater than 0.2 micron or at least 90% in number in which are not gerater than 0.25 micron in grain size and at least one sensitizing base represented by the following general formula (I);
 13. The emulsion as claimed in claim 12 where 1, if substituted, is substituted with a chlorine atom.
 14. The emulsion as claimed in claim 12 where the amount of base(s) is about 1 X 10 3 to about 1 X 10 5 mol/mol of silver in the emulsion.
 15. The emulsion as claimed in claim 14 where the emulsion comprises gelatin as a hydrophilic binder.
 16. The emulsion as claimed in claim 1 where R3 represents an alkyl group.
 17. The emulsion as claimed in claim 16 wherein R3 represents an alkyl group of up to 4 carbon atoms.
 18. The emulsion as claimed in claim 2 wherein R3 represents an alkyl group.
 19. The emulsion as claimed in claim 18 wherein R3 represents an alkyl group with up to 4 carbon atoms.
 20. The emulsion as claimed in claim 12 wherein R3 represents said alkyl group with up to 4 carbon atoms. 